1. Field of the Invention
The present invention relates to photovoltaic modules for converting light into electrical energy. More particularly, the present invention relates to a method of applying a photo-catalyst semiconductor material onto a front substrate of a photovoltaic module, which offers significant advantages in terms of dustproofing and weather resistance.
2. Description of the Related Arts
The world supply of fossil fuels is dwindling, and the combustion of such fossil fuels is environmentally unfriendly; although the nuclear power can meet electricity needs, there are significant issues in terms of the safety of nuclear radiation and storage of the nuclear waste. For these reasons, there is a demand for alternative energy sources with low or no pollution. The photovoltaic module, capable of converting solar energy into eLectricity, is an example of one of such sources.
The application of photovoltaic modu es can be broadly classified as: (1) small-scale consumer products such as calculators, watches and toys etc.; and (2) middle- or large-scale AC/DC power supplies such as beacon lamps, remote telecommunications relays, and auxhliary power supplies of electric network etc. The types of photovoltaic modules can be classified as: (1) single- or polycrystalline silicon photovoltaic modules, which because of the mature technology hold a market share exceeding 75%; (2) novel amorphous silicon photovoltaic modules, which primarily apply to consumer products and have a market share of 10%; and (3) photovoltaic modules produced by other materials, which due to problems in large-area production, remain in the stage of research and development.
The most common structure of a crystalline silicon photovoltaic module consists of 3 major layers, in which the material of each layer is selected based on its function. Generally, the front substrate is a heat-treated safety glass plate, which transmits light, and maintains the integrity and durability of the photovoltaic modules under the operating environment. Beneath the front substrate is a photosensitizer, which is mounted by layers of ethylene vinyl acetate (hereinafter referred as EVA). The EVA possesses the functions of connecting electric circuits, insulating the circuit from electric conductivity and environment, providing appropriate mechanical strength and providing pathways for thermal conducting etc. The back substrate is generally TEDLAR .RTM. (TEDLAR.RTM. is a trademark of E.I. Du Pont De Nemours and Company) polymer membrane or glass, which must withstand the rigors of the environment and hydrolysis under such an environment.
It is believed that the soldering of electric circuits onto the electrodes of photovoltaic modules, appropriately enclosing the series or parallel connected photovoltaic modules, and processing the surface of the glass to protect the modules from environment and thus to prolong the life-span thereof, are the keys for increasing the quality and durability of photovoltaic modules.
In the previous technology, titanium dioxide is used in the photosensitizer for promoting the converting efficiency of photovoltaic modules (see, e.g. U.S. Pat. No. 5,350,644). The technique has the following disadvantages: the air pollutants adhere to the surfaces of photovoltaic modules and obstruct the transmittance of light after a period of time, and thus restrict the energy source of photovoltaic modules. Further, titanium dioxide mixed with fluorides resin has been applied to the surfaces of photovoltaic modules. However, the process is more complex, and titanium dioxide may interact with fluorides resin such that the quality of titanium dioxide will be limited, or the adhesion and uniformity of the applied mixture wile be affected (also see, e.g. Japan Patent Nos. 9-313,934A and 10-270,732A).